The present invention relates to a shell or missile having a shell body and guiding means being radially protrudingly arranged for guiding the shell body in a gun barrel. The invention also relates to a process for the preparation of radially protruding guiding means on a shell body of a shell to be guided in a gun barrel.
Known shells typically have a guiding means made of copper 15 attached to the external surface area of the shell. There are also known shells having several guiding means being arranged in a defined distance to each other in the form of ring-shaped elevations. When such a formed shell body is launched from a gun barrel whose inner surface contains several helicoidally revolving grooves, the elevations are squeezed and formed, by which the shell receives a rotation that serves to stabilize the shell on its flight path. At the same time the guiding means serve to tighten and bind the shell within the barrel against the hot powder gases impinging on the rear side of the shell and form an anti-attrition interface layer between the shell body and the gun barrel.
For the preparation of these known guiding means a circumferential groove is turned into the shell body, wherein a ring is shrinked, pressed and/or anchored by welding.
A disadvantage of the known shells is that they can drag-in copper into the gun barrel surface at firing. This can ultimately lead to an embrittlement of the gun barrel and results in a reduction of its mechanical stability. After a number of firings, depending on different initial conditions, the gun barrel is no longer serviceable. The drag-in of copper into the system""s environment is also problematic, especially with ammunition that is intended for exercise purpose use.
Moreover, the high gas pressures of modem weapon systems lead to dynamic loads which such copper rings often cannot successfully resist.
The present invention is therefore directed to a new and improved shell of the general type set forth, which avoids to a large extent a drag-in of copper into the gun barrel and its surroundings at firing. Moreover, the invention provides a process for the production of radially protruding guiding means in such a way that an optimal bonding of the guiding means to the shell body is achieved, whereby the transition zone between both parts can be optimizable or minimizable as appropriate. The invention also allows extremely high temperatures and gas pressure loads to arise on the guiding means without causing them to fail.
In accordance with the foregoing purposes and to solve deficiencies in the prior art, the present invention provides guiding means in which at least the radially outer area of the guiding means contains nickel.
By this structure it becomes possible to substantially reduce the copper content almost at least in the region of the shell body touching the gun barrel at launch. In this way a release of copper from the guiding means can be reliably avoided. A shell according to the invention thus avoids at its launch the drag-in of copper into the gun barrel and its surrounding. Contamination and/or reduction of the abrasion resistance at the inner surface of the gun barrel by reduction of its stability and by embrittlement due to metallurgic interaction is also thereby reliably avoidable.
The guiding means can be produced particularly economically according to another advantageous further development of the invention, in which the radially outer area of the guiding means is shaped as a nickel-containing layer attached to the basic body. The shell body has, in the area of the guiding means, a particularly high stability when the material of the basic body is made of tempered steel or maraging steel.
The connection between the nickel-containing layer and the basic body can be produced according to another advantageous further development of the invention particularly economically, when the guiding means are materially fitted to the basic body. For the material fitting the welding process is particularly suitable.
The nickel-containing layer may, for example, be applied on a rotating band. The rotating band may be subsequently connected to the shell body just as known in the art. Alternatively, however, a reduction of production costs of the shell according to the invention may be possible when the guiding means are arranged directly on the shell body.
Tests have shown that the guiding means have a particularly high stability when their nickel content amounts to more than 90%. Preferably, the guiding means consist of nickel of high purity having a nickel content of more than 99%.
The creation of the process for the production of radially protruding guiding means in such a way that the drag-in of copper into the gun barrel can be avoided therewith is addressed by the present invention by the application of a single layer containing nickel onto a basic body. By this method the copper content of the radially outer area of the guiding means can be limited to predetermined acceptable dimensions or can be completely avoided. Since the only radially outer area of the guiding means touches the gun barrel at shell launch, the transfer of copper from the guiding means to the gun barrel can reliably be avoided even when the shell body itself contains copper. The shell according to the invention thus avoids to a large extent at launch the drag-in of copper into the gun barrel. Embrittlement of the gun barrel is also reliably avoided. The basic body can alternatively be the shell body itself or a rotating band to be connected to the shell body.
The production of the guiding means according to the invention is particularly economical when the application of the nickel containing layer is made by a build-up welding process. Further, the guiding means can have particularly large dimensions.
Disadvantageous changes to the metallic structure or even fissures and micro hollow spaces in the connection of the nickel containing layer with the basic body, as a rule made out of a steel alloy, can be avoided to a large extent according to a further advantageous development of the invention, namely when the basic body is exposed to a protective gas atmosphere at 815 degrees C. during one to three hours following the build up welding process. By this heat treatment damage in the basic body produced by the welding can regress and the structure of the material of the basic body can be homogenized. By suppression of the fissures and the micro hollow spaces a shearing off of the guiding means at launch of the shell can reliably be avoided. Additionally, changes to the metallic structure, leading to a reduction of the mechanical resistance of the shell body under dynamic stress, can be undone. As the protective gas argon is particularly suitable.
According to a further advantageous development of the invention a contribution to the further reduction of the fissures and micro hollow spaces may be achieved when the basic body is exposed to a protective gas atmosphere during three to six hours at 480 degrees C. By this treatment the basic material undergoes a further increase in stability. This heat treatment preferably follows an intermediate cool down phase to room temperature after the first heat treatment at 815 degrees C.
Required tolerances of the guiding means can efficiently be met according to a further advantageous aspect of the invention, when the nickel-containing layer is shaped by metal-cutting to the planned dimensions after the build-up weld. This treatment by metal-cutting can be effected, for example, by a turning process.